In a manufacturing process of an AMOLED (active-matrix organic light-emitting diode) array substrate, indium gallium zinc oxide (InGaZnO4; IGZO), an oxide semiconductor, due to its high mobility, good uniformity and capability of being prepared at room temperature, is used as material of an active layer of a thin film transistor, and the thin film transistor generally has a bottom-gate type structure.
FIG. 1 shows the most basic 2T1C pixel structure, which comprises: two thin film transistors (i.e., a first thin film transistor M1 and a second thin film transistor M2) and one storage capacitor C1, and a source of the first thin film transistor M1 is connected to a gate of the second thin film transistor M2.
As shown in FIGS. 2 and 3, in manufacturing an AMOLED array substrate having a 2T1C structure, sources and drains 106 of the first and second thin film transistors M1 and M2 are connected to the respective active regions 103 thereof through second contacting vias 105, respectively, and the gate 102 of the second thin film transistor (driving tube) M2 and the source 106 of the first thin film transistor (switching tube) M1 are connected through a first contacting via 104; by adjusting gate voltage of the second thin film transistor M2 (i.e., source voltage of the first thin film transistor M1), magnitude of current passing through the second thin film transistor M2 can be controlled, and thus a light emission amount from an organic light-emitting layer corresponding to each pixel unit is controlled. However, in the manufacturing process of the above AMOLED device, the technician found that electricity leakage always occurs on an AMOLED backplane (array substrate), which badly affects the yield rate of products.
In an AMOLED display device adopting bottom-gate type TFTs, taking a case that 2T1C is adopted as an example, in one same pixel unit, the first thin film transistor M1 serves as the switching tube, the second thin film transistor M2 serves as the driving tube, and the source of the switching tube and the gate of the driving tube need to be electrically connected through a contacting via. With respect to the problem of electricity leakage occurring on an AMOLED backplane (array substrate) in an existing AMOLED display device, inventors of the present invention have found the followings.
In the manufacturing process of the first contacting via 104 and the second contacting via 105, one exposure and development (Mask-Photo) process is generally used to form patterns of two types of contacting vias on photoresist, and then the two types of contacting vias are formed through one dry etching process. However, in the process of etching, since an etching depth required by the first contacting via 104 is far larger than that of the second contacting via 105, etching time is too long for the second contacting via 105. Long-time dry overetching at the second contacting via 105 may cause the material of the active region 103 and a gate insulation layer provided between the active region 103 and the gate 102 to be further etched until fractured, which causes the source and drain 106 deposited in the subsequent process to be connected to the gate 102 located at the bottom, thus resulting in serious electricity leakage of the backplane. Consequently, the backplane is eventually scrapped and the yield rate is lowered.
Of course, the first contacting via 104 and the second contacting via 105 may be formed through two separate patterning processes, but this method has complex processes and low production efficiency.